1. Field of the Invention
The present invention relates to an insulating apparatus, and more especially, to an insulating apparatus used in a connecting wire of an suppression electrode of an ion implanter.
2. Description of the Prior Art
Ion implantation is a widely used technique in the semiconductor industry, in which energetic, charged atoms or molecules are directly introduced into a substrate. In an integrated circuit fabrication, ion implantation is primarily used to add dopant ions into the surface of silicon wafers. Most of the impurity-doped regions, such as N-type and P-type well regions, source and drain regions, channel stop regions, and doped polysilicon electrode, can be fabricated by ion implantation, with or without the process of drive-in.
Typically, an ion implanter system, which is used to carried out the ion implantation process, comprises a ion source, an extraction device, a mass analysis, an accelerator, a scanning system, and other attached equipment such as gas delivery system, high vacuum system, and so on. In this ion implanter system, the ion source, which is generally an arc chamber, is used to ionize the source gases to form the ion gases. The ionized gases are extracted from the source chamber by an extraction electrode assembly. The extracted ion beam passes by a mass analysis, and the ions of undesired species are filtered out according to their masses. The accelerator creates an acceleration field to increase the ion energy to a desired level, and the scanning system distributes the ions uniformly over the target.
FIG. 1 depicts a portion of an ion implanter, including an ion source as an arc chamber 10 and an extraction electrode assembly 20. The arc chamber 10 is basically a DC plasma generator, which accesses source gases from a gas feeding system not shown in the figure. The source gases are ionized in the arc chamber 10 through collision with electrons from an arc discharge, which is typically a hot filament. After the ionized plasma gases is generated, the extraction electrode assembly 20 is applied to extract the ionized gases out from the arc chamber 10.
The extraction electrode assembly 20 consists essentially of an extraction electrode 22 and a suppression electrode 24, with proper insulator deposed between them. The extraction electrode 22 is grounded to provide a voltage relatively lower than that of the arc chamber, which usually maintains at the level of tens of kilo voltage during operation. The positive ions in the arc chamber are therefore attracted by the lower voltage and move toward the extraction electrode 22 out from the arc chamber 10. Being adjusted and focused, the extracted ion beam passes the extraction electrode assembly 20 through a slit 26 therein, with the direction indicated by the arrow 30, and then flow toward the mass analysis and accelerator disposed downstream.
To focus and adjust the extracted ion beam, a suppression power with high negative voltage of about -1.8 KV is applied to the suppression electrode 24 deposed in the extraction electrode assembly 20. The suppression electrode 24 typically comprises a graphite plate 34, a metal plate 36 and a conductive rod assembly 38 connecting between them. The graphite plate 34 can provide the protection to the metal from the attack of the extracted ions to prevent damages and the generation of X-ray. With the electric field created by the suppression voltage, the extracted ion beam can be adjusted and prevented from blow-up (in the other words, be focused), and the arrival of unwanted electrons to the linear acceleration area, which is created by the accelerator downstream, can be suppressed.
To implement the focusing of the extracted ion beam, the suppression electrode 24 is secured to the extraction electrode assembly 20 as an integral device, and a supporting arm 32 is mounted to the grounded extraction electrode 22, to provide support, grounded connection, and the capability of position adjustment. When the supporting arm 32 moves, the positions of the electrodes, and thus the slit 26 and the suppression electric field is regulated to adjust the ion beam.
For providing suppression power to the suppression electrode 24, a conductive line 50 extends from a power source 60 to the suppression electrode 24, in connection with one of the conductive rods 38. The conductive line 50 is typically a coil with a certain cross section area. In the high-energy ion implanter EATON HE from EATON Inc., the conductive line 50 of coil type is disposed across the supporting arm 32 as shown in FIG. 2. In this configuration, the conductive line 50 is easy to form a short circuit with the grounded supporting arm 32, when the supporting arm 32 is operated to adjust the extraction electrode assemble 20. Once the short circuit phenomenon occurs, the suppression current will become very large, and the ion beam can not be focused any more. The implanter thus goes wrong. To set the machine right, it needs to shutdown the machine, vent the chamber pressure to atmosphere, and disassembly the electrode to adjust the power wire. These works takes a lot of time and will cause great loss of efficiency.